Enhancing juror understanding of probabilistic DNA evidence

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DNA experts, researchers, and legal professionals agree that laypersons experience difficulty understanding and applying aspects of DNA expert evidence. This paper reviews empirical research on documented problems that jurors experience in response to probabilistic forensic evidence. A 2x2 between subjects study tested the sensitivity of 200 mock jurors to the probative value of DNA evidence with and without error rates, and the efficacy of a post-trial judicial caution intended to prevent jurors from assigning undue weight to the DNA evidence. When DNA evidence was included in a weak, circumstantial criminal case, although the majority of the participants voted to acquit, the conviction rate increased significantly. However, participants were insensitive to variations in the probative weight of a probabilistic DNA match in the context of error rates. Contrary to expectations, the model judicial caution on applying the DNA evidence failed to reduce the rate of convictions or perceived factual guilt. These results suggest that DNA evidence can be influential, but that jurors are not overwhelmed by its presence. Jurors may benefit more from pre-trial training and presentation of the judicial caution earlier in the trial. Additional research is needed on techniques to assist jurors in more appropriately evaluating and applying probabilistic expert evidence.
Original languageEnglish
Pages (from-to)86-96
Number of pages11
JournalAustralian Journal of Forensic Sciences
Issue number2
Publication statusPublished - 2006

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